Disazo dyes, and copper complexes thereof, for dyeing paper

ABSTRACT

The dyes of formula (1) according to claim  1  and the copper complexes of dyes of formula (2) according to claim  9  or the mixtures of mono-copper complex with the bis-copper complex are excellently suitable for dyeing paper with good light-fastness properties.

The present invention relates to dyes of formula

wherein

-   Z₁ is NHR₆, -   R₆ being a radical of formula CO—R₈, CO—NH—R₈, SO₂-alkyl, SO₂-aryl,

-   COOR₈, -   R₈ being hydrogen, alkyl or aryl and -   R₇ being COOH or SO₃H in the o-position to the NH₂ group, -   Z₂ is as defined for Z₁ or is hydrogen, hydroxy, alkoxy or a radical     NHR₅, -   R₅ being hydrogen, alkyl, aryl, COR₈, CO—NHR₈ or SO₂R₈, -   R₁ and R₃ are each independently of the other hydrogen, hydroxy,     alkyl or alkoxy, -   R₂ and R₄ are each independently of the other hydrogen, hydroxy,     alkyl or alkoxy, halogen, sulfo, carboxy, NHCONHR₈ or NHCOR₈, -   X is a direct bond in which case symmetrical compounds wherein Z₁     and Z₂ are NHCOCH₃, NHCOOCH₃ or NHCO-phenyl are excluded, or is     —C═C— in which case both Z₁ and Z₂ cannot simultaneously be     acetylamino, benzoylamino or 4-amino-3-sulfo-anilino, or is azo,     azoxy, —NR₈, —NR₈CONR₉— or a group of formula

-   Y being hydroxy, alkoxy or NR₈R₁₀, -   R₉ and R₁₀ being each independently of the other hydrogen,     unsubstituted or substituted alkyl or unsubstituted or substituted     aryl, -   n and m are each independently of the other 1 or 2, -   and wherein the rings A and B may each independently of the other     carry a fused-on benzene ring, -   with the proviso that the compounds of formulae

are excluded.

The present invention relates also to mono- or bis-copper complexes of dyes of formula

wherein R₁ and/or R₃ are hydroxy or alkoxy and the other substituents are as defined for formula (1).

In this Application, the dyes are shown in the form of the free acid, but the corresponding salts, for example metal or ammonium salts, are also to be included.

In the dyes of formula (1), X is preferably azo, azoxy or —C═C—.

In this Application, halogen is generally fluorine, bromine or, especially, chlorine.

According to the invention, alkyl radicals are to be understood as being generally open-chain or branched or cyclic alkyl radicals, preferably containing from 1 to 8 carbon atoms, for example methyl, ethyl, n- or iso-propyl, n-, sec- or tert-butyl, n-hexyl, n-octyl, cyclopentyl and cyclohexyl.

Aryl is to be understood as being especially naphthyl or phenyl, each of which may be substituted by, for example, C₁–C₄alkyl, and more especially unsubstituted naphthyl or phenyl.

These alkyl radicals and also the cycloalkyl or aryl groups may be mono- or poly-substituted, for example by hydroxy, carboxy, halogen, cyano, amino or C₁–C₄alkoxy.

The alkoxy radicals may have from 1 to 12 carbon atoms, preferably from 1 to 4 carbon atoms and are, for example, methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, n-pentyloxy and n-hexyloxy. The alkoxy groups also may be substituted, for example by the radicals listed as possible substituents for the alkyl groups, especially by hydroxy or C₁–C₄alkoxy.

In the dyes of formula (1) and copper complexes thereof, Z₂ is preferably hydrogen, hydroxy, alkoxy, amino, NH—COO—C₁–C₄alkyl, or anilino which is unsubstituted or substituted by amino and/or by sulfo.

Z₁ is preferably NH—COO—C₁–C₄alkyl or the 4-amino-3-sulfo-anilino radical.

R₂ and R₄ are preferably hydrogen, C₁–C₄alkyl or C₁–C₄alkoxy.

In especially preferred dyes, Z₁ and Z₂ are identical and each is NH—COO—C₁–C₄alkyl or the 4-amino-3-sulfo-anilino radical.

The dyes of formula (1) are prepared in a manner known per se, for example a diamine of formula

is tetraazotised in known manner and coupled with 2 moles of a coupling component of formula

or with 1 mole each of a coupling component of formula (4) and a coupling component of formula

under conditions known per se.

It is also possible first to prepare the monoazo compounds of formulae

and to react 2 moles of a compound of formula (6) or 1 mole of a compound of formula (6) and 1 mole of a compound of formula (7) with a compound U—X—U′, QH and Q′H in each case being a group which can be replaced with a bridging member of formula X with removal of UH and U′H, respectively.

Such reactions have been described many times in the literature for the preparation of bridged disazo dyes.

When X is an azoxy group, the corresponding compounds of formula (1) can also be prepared in a manner likewise known per se by diazotisation of unsubstituted or substituted p-nitroanilines, coupling with a coupling component of formula (4) and/or (5) and subsequent reduction, for example using glucose.

The dyes of formula (1) which contain a free amino group can, in many cases, be prepared in pure form only with difficulty. An improvement can be achieved by introducing a protecting group which is subsequently removed. That is the case especially for those dyes wherein X is azoxy. Suitable protecting groups are those that are readily removable and that are stable under the conditions of the basic azoxy condensation. An alkoxycarbonyl group, especially the ethoxycarbonyl group, is especially suitable.

The mono- or bis-copper complexes of dyes of formula (2) are obtained in a manner known per se by means of copper-treatment of the customarily prepared dyes of formula (1) using copper-yielding agents in amounts of from 1 to 2.5 moles of copper per mole of dye of formula (1). The copper-treatment can also be carried out by demethylation as a result of cleavage of an alkoxy group or oxidatively with introduction of an additional oxygen group.

The invention preferably relates to the mono-copper complexes of dyes of formula (2) and mixtures thereof with the bis-copper complexes of such dyes.

These are obtained in a manner known per se by means of copper-treatment of the conventionally prepared dyes of formula (2) using copper-yielding agents in amounts of from 1 to 1.5 moles of copper per mole of dye of formula (2).

Depending upon the nature of the bridging member X, it is also possible for one of the halves of the dye of formula (2) that are connected by X to be reacted with up to 1 mole of copper-yielding agent and then to be connected to the second, non-copper-treated half by a direct bond or via the bridging member X. It is preferred, however, to start from the dye of formula (2) and to react that dye with a copper-yielding agent.

The dyes of formula (1) and the mono- and bis-copper complexes of dyes of formula (2) are suitable for dyeing natural and synthetic material.

The material is, for example, fibre material of leather, wool, polyamide, glass fibres or cotton and, especially, paper.

Using customary dyeing methods, blue dyeings having good fastness properties are obtained on such materials. Dyeings using the copper complexes especially have excellent light-fastness properties. The shade and the light-fastness can be controlled by the amount of copper used. When preparing mixtures of the mono-copper complexes with the bis-copper complexes, the amount of free copper in the effluents from synthesis can be reduced to a value of under 100 ppm whilst still obtaining good light-fastness properties.

The invention relates also to the use, for dyeing paper, of dyes of formula

wherein

-   Z′₁ is NHR₆, -   R₆ being a radical of formula CO—R₈, CO—NH—R₈, SO₂-alkyl, SO₂-aryl,

-   COOR₈, -   R₈ being hydrogen, alkyl or aryl and -   R₇ being COOH or SO₃H in the opposition to the NH₂ group, -   Z′₂ is as defined for Z′₁ or is hydrogen, hydroxy, alkoxy or a     radical NHR₅, -   R₅ being hydrogen, alkyl, aryl, COR₈, CO—NHR₈ or SO₂R₈, -   R₁ and R₃ are each independently of the other hydrogen, hydroxy,     alkyl or alkoxy, -   R₂ and R₄ are each independently of the other hydrogen, hydroxy,     alkyl or alkoxy, halogen, sulfo, carboxy, NHCONHR₈ or NHCOR₈, -   X Is a bridging member or a direct bond, -   n and m are each independently of the other 1 or 2, -   and wherein the rings A and B may each independently of the other     carry a fused-on benzene ring, it not being possible for both Z′₁     and Z′₂ simultaneously to be acetylamino or benzoylamino when X is a     bridging member of formula —C═C—, and with the proviso that the     compound of formula

is excluded.

The dyes of formula (1) and the copper complexes of dyes of formula (2) or the mixtures of mono-copper complex with the bis-copper complex are preferably used as solid or liquid commercial forms.

In the form of powder or granules, the dyes are used especially in discontinuous mass dyeing, the dyes being added usually in the form of a stock solution to the pulper, hollander or mixing vat. In this case dye preparations are preferably used which may also comprise, besides the dye, diluents, e.g. urea as solubiliser, dextrin, Glauber's salt, sodium chloride and dispersants, dusting agents and sequestrants, such as tetrasodium phosphate.

The invention accordingly relates also to solid dye preparations for dyeing paper, which preparations comprise a dye of formula (1) according to the invention or a mono- or bis-copper complex of a dye of formula (2).

In recent years, the use of concentrated aqueous solutions of dyes has gained in importance, specifically because of the advantages which such solutions have over dyes in powder form. By using solutions, the difficulties associated with the formation of dust are avoided and the users are freed from the time-consuming and often difficult dissolution of the dye powder in water. The use of concentrated solutions has been prompted furthermore by the development of continuous dyeing processes for paper, since in those processes it is advantageous to add the solution in metered amounts directly to the pulp flow or at any other suitable point in the paper-making.

The invention accordingly relates also to concentrated aqueous solutions of the dyes of formula (1) used in accordance with the invention or of the mono- or bis-copper complexes of dyes of formula (2) for dyeing paper, which solutions contain from 5 to 30% by weight of dye, based on the total weight of the solution.

The concentrated solutions may comprise further auxiliaries, for example solubilisers, such as ε-caprolactam or urea, organic solvents, such as glycols, polyethylene glycols, dimethyl sulfoxide, N-methylpyrrolidone, acetamide, alkanolamines or polyglycolamines.

The following Examples serve to illustrate the invention but do not limit the invention thereto. Parts and percentages relate to weight, unless otherwise indicated.

EXAMPLE 1

127.6 parts of 1-amino-8-naphthol-3,6-disulfonic acid are dissolved in 600 parts of water containing 30% sodium hydroxide solution at pH 6.5 to 7; the solution is then adjusted to a pH of 2.5 using 32% hydrochloric acid and stirred to form a homogeneous suspension. Starting at a temperature of 5° C., 54 parts of chloroformic acid ethyl ester are added dropwise over 1 hour, in the course of which the temperature rises to about 32° C., the pH being maintained at 2.5 by the dropwise addition of 30% sodium hydroxide solution. Heating at 35° C. is carried out until no more sodium hydroxide solution is used.

In a separate vessel, 16.8 parts of 2-amino-5-nitroanisole are diazotised in 100 parts of water containing 32% hydrochloric acid and sodium nitrite. The reaction solution is then coupled with 43 parts of the above-described 1-ethoxycarbonyl-8-naphthol-3,6-disulfonic acid in 170 parts of water at room temperature and pH 7 with addition of 30% sodium hydroxide solution. The suspension obtained is heated to a temperature of from 50 to 60° C.; 110 parts of 30% sodium hydroxide solution are added and, in the course of 1 hour, a solution of 15 parts of glucose in 60 parts of water is added. As soon as no more starting material is detectable, the pH is adjusted to 7.5 using 32% hydrochloric acid, with cooling, salted out with 60 parts of sodium chloride and filtered. The dye of formula

is obtained. It dyes cellulose fibres, especially paper, brilliant reddish-blue shades having good fastness properties and with a high degree of exhaustion.

EXAMPLES 2–11

By proceeding as described in Example 1, but using the coupling components listed in the following Table, dyes are obtained that have similarly good properties, especially when dyeing paper.

Example Coupling Component 2 1-methoxycarbonylamino-8-naphthol-3,6-disulfonic acid 3 1-ethoxycarbonylamino-8-naphthol-2,4-disulfonic acid 4 1-ethoxycarbonylamino-8-naphthol-4,6-disulfonic acid 5 2-ethoxycarbonylamino-5-naphthol-1,7-disulfonic acid 6 3-ethoxycarbonylamino-5-naphthol-2,7-disulfonic acid 7 2-ethoxycarbonylamino-5-naphthol-7-sulfonic acid 8 3-ethoxycarbonylamino-5-naphthol-7-sulfonic acid 9 2-ethoxycarbonylamino-5-naphthol-4,8-disulfonic acid 10 2-(4-amino-3-sulfo-anilino)-5-naphthol-7-sulfonic acid 11 3-(4-amino-3-sulfo-anilino)-5-naphthol-7-sulfonic acid

EXAMPLE 12

28 parts of 4,4′-diamino-3,3′-dimethoxy-azobenzene are tetraazotised in 200 parts of water containing 40 parts of 32% hydrochloric acid and 50 ml of 4N sodium nitrite solution at 0–5° C. Then, at 10–20° C., coupling to 86 parts of 2-ethoxycarbonylamino-5-naphthol-1,7-disulfonic acid, dissolved in 250 parts of water, is carried out, the pH being maintained at 7.5–8 by the addition of 30% sodium hydroxide solution. Then, salting-out using 80 parts of sodium chloride and filtration are carried out. A dye is obtained that has similarly good properties to the dye described in Example 1.

EXAMPLES 13–62

By proceeding as described in Example 12, but using the diamines listed in the following Table together with 2 equivalents of the listed coupling components, dyes are obtained that have similarly good properties, especially when dyeing paper. It is also possible, in a manner known per se, first to react the first diazo group of the diamine with a first coupling component and then to react the second diazo group with a second coupling component.

Example Diamine Coupling Component 13 4,4′-diamino-3,3′-dimethoxy- 1-ethoxycarbonylamino-8- azobenzene naphthol-3,6-disulfonic acid 14 4,4′-diamino-3,3′-dimethoxy- 1-methoxycarbonylamino-8- azobenzene naphthol-3,6-disulfonic acid 15 4,4′-diamino-3,3′-dimethoxy- 3-ethoxycarbonylamino-5- azobenzene naphthol-2,7-disulfonic acid 16 4,4′-diamino-3,3′-dimethoxy- 2-ethoxycarbonylamino-5- azobenzene naphthol-1,7-disulfonic acid 17 4,4′-diamino-3,3′-dimethoxy- 2-ethoxycarbonylamino-5- azobenzene naphthol-4,8-disulfonic acid 18 4,4′-diamino-3,3′-dimethoxy- 2-(4-amino-3-sulfo-anilino)-5- azobenzene naphthol-7-sulfonic acid 19 4,4′-diamino-3,3′-dimethoxy- 1st coupling comp.: 2-ethoxy- azobenzene carbonylamino-5-naphthol-7- sulfonic acid 2nd coupling comp.: 2- ethoxycarbonylamino-5- naphthol-1,7-disulfonic acid 20 4,4′-diamino-azobenzene 1-ethoxycarbonylamino-8- naphthol-3,6-disulfonic acid 21 4,4′-diamino-2′-methyl- 1-ethoxycarbonylamino-8- azobenzene naphthol-3,6-disulfonic acid 22 4,4′-diamino-2′-methyl- 3-ethoxycarbonylamino-5- azobenzene naphthol-1,7-disulfonic acid 23 4,4′-diamino-2′-methyl- 1st coupling comp.: 1- azobenzene naphthol-3,6-disulfonic acid 2nd coupling comp.: 2- ethoxycarbonylamino-5- naphthol-7-disulfonic acid 24 4,4′-diamino-2′-methyl- 2-ethoxycarbonylamino-5- azobenzene naphthol-4,8-disulfonic acid 25 4,4′-diamino-2′-methyl- 2-(4-amino-3-sulfo-anilino)-5- azobenzene naphthol-7-sulfonic acid 26 4,4′-diamino-2′,5′-dimethyl- 1-ethoxycarbonylamino-8- azobenzene naphthol-3,6-disulfonic acid 27 4,4′-diamino-2′,5′-dimethyl- 2-ethoxycarbonylamino-5- azobenzene naphthol-1,7-disulfonic acid 28 4,4′-diamino-3′-methoxy- 1-ethoxycarbonylamino-8- azobenzene naphthol-3,6-disulfonic acid 29 4,4′-diamino-3′-methoxy- 2-ethoxycarbonylamino-5- azobenzene naphthol-1,7-disulfonic acid 30 4,4′-diamino-2′-methoxy- 1-ethoxycarbonylamino-8- azobenzene naphthol-3,6-disulfonic acid 31 4,4′-diamino-2′-methoxy- 2-ethoxycarbonylamino-5- azobenzene naphthol-1,7-disulfonic acid 32 4,4′-diaminostilbene 1-ethoxycarbonylamino-8- naphthol-3,6-disulfonic acid 33 4,4′-diaminostilbene 1-methoxycarbonylamino-8- naphthol-3,6-disulfonic acid 34 4,4′-diaminostilbene 3-ethoxycarbonylamino-5- naphthol-2,7-disulfonic acid 35 4,4′-diaminostilbene 2-ethoxycarbonylamino-5- naphthol-1,7-disulfonic acid 36 4,4′-diaminostilbene 2-ethoxycarbonylamino-5- naphthol-4,8-disulfonic acid 37 4,4′-diaminostilbene 2-(4-amino-3-sulfo-anilino)-5- naphthol-7-sulfonic acid 38 4,4′-diamino-3,3′-dimethoxy- 1-ethoxycarbonylamino-8- stilbene naphthol-3,6-disulfonic acid 39 4,4′-diamino-3,3′-dimethoxy- 2-ethoxycarbonylamino-5- stilbene naphthol-1,7-disulfonic acid 40 4,4′-diamino-3-methoxy- 1-ethoxycarbonylamino-8- stilbene naphthol-3,6-disulfonic acid 41 4,4′-diamino-3-methoxy- 2-ethoxycarbonylamino-5- stilbene naphthol-1,7-disulfonic acid 42 4,4′-diaminostilbene-2,2′- 2-ethoxycarbonylamino-5- disulfonic acid naphthol-7-sulfonic acid 43 4,4′-diaminostilbene-2,2′- 1st coupling comp.: 3-ethoxy- disulfonic acid carbonylamino-5-naphthol-7- sulfonic acid 2nd coupling comp.: 1-amino- 8-naphthol-3,6-disulfonic acid 44 4,4′-diamino-diphenylamine 1-ethoxycarbonylamino-8- naphthol-3,6-disulfonic acid 45 4,4′-diamino-diphenylamine 1-acetylamino-8-naphthol-3,6- disulfonic acid 46 4,4′-diamino-diphenylamine 1-ureido-8-naphthol-3,6- disulfonic acid 47 4,4′-diamino-diphenylamine 1-methylsulfonylamino-8- naphthol-3,6-disulfonic acid 48 4,4′-diamino-diphenylamine 1-phenylsulfonylamino-8- naphthol-3,6-disulfonic acid 49 4,4′-diamino-diphenylamine 1-p-tolylsulfonylamino-8- naphthol-3,6-disulfonic acid 50 4,4′-diamino-2-sulfo- 1st coupling comp.: 3-ethoxy- diphenylamine carbonylamino-2-naphthol-7- sulfonic acid 2nd coupling comp.: 1-amino- 8-naphthol-3,6-disulfonic acid 51 4,4′-diamino-3,3′-dimethoxy- 1-ethoxycarbonylamino-8- diphenylurea naphthol-3,6-disulfonic acid 52 4,4′-diamino-3,3′-dimethoxy- 1-acetylamino-8-naphthol-3,6- diphenylurea disulfonic acid 53 4,4′-diamino-3,3′-dimethoxy- 1-ureido-8-naphthol-3,6- diphenylurea disulfonic acid 54 4,4′-diamino-3,3′-dimethoxy- 1-methylsulfonylamino-8- diphenylurea naphthol-3,6-disulfonic acid 55 4,4′-diamino-3,3′-dimethoxy- 1-phenylsulfonylamino-8- diphenylurea naphthol-3,6-disulfonic acid 56 4,4′-diamino-3,3′,2,2′- 1-ethoxycarbonylamino-8- tetramethoxy-diphenylurea naphthol-3,6-disulfonic acid 57 2,4-di(3′-methoxy-4′-amino- 1-ethoxycarbonylamino-8- phenyl-amino)-6-di(2′- naphthol-3,6-disulfonic acid hydroxy-ethyl-amino)-1,3,5- triazine 58 2,4-di(3′-methoxy-4′-amino- 1-acetylamino-8-naphthol-3,6- phenyl-amino)-6-di(2′- disulfonic acid hydroxy-ethyl-amino)-1,3,5- triazine 59 2,4-di(3′-methoxy-4′-amino- 1-ureido-8-naphthol-3,6- phenyl-amino)-6-di(2′- disulfonic acid hydroxy-ethyl-amino)-1,3,5- triazine 60 2,4-di(3′-methoxy-4′-amino- 1-methylsulfonylamino-8- phenyl-amino)-6-di(2′- naphthol-3,6-disulfonic acid hydroxy-ethyl-amino)-1,3,5- triazine 61 2,4-di(3′-methoxy-4′-amino- 1-phenylsulfonylamino-8- phenyl-amino)-6-di(2′- naphthol-3,6-disulfonic acid hydroxy-ethyl-amino)-1,3,5- triazine 62 4,4′-diamino-3,3′-dimethoxy- 1st coupling comp.: 1-ethoxy- biphenyl carbonyl-amino-8-naphthol- 3,6-disulfonic acid 2nd coupling comp.: 2-(4- amino-3-sulfoanilino)-5- naphthol-7-sulfonic acid

EXAMPLES 63–68

The dyes described in Examples 28, 29, 40 and 41 are converted, in a manner known per se, into the mono-copper complexes, by means of “demethylating copper-treatment”. These complexes are especially suitable for dyeing paper with good fastness properties.

EXAMPLES 69–102

The dyes described in Examples 1–19, 38, 39 and 51–62 are converted, in a manner known per se, into the bis-copper complexes, by means of “demethylating copper-treatment”. These complexes are especially suitable for dyeing paper with good fastness properties.

EXAMPLE 103

100 parts of 50% sodium hydroxide solution are added to the crude synthesis solution of the dye described in Example 2 and stirring is carried out for 3 hours at a temperature of from 90 to 95° C. until hydrolysis is complete.

Neutralisation is then carried out using 32% hydrochloric acid and the precipitated dye is filtered off at room temperature. Without further purification operations, there is obtained, in a very high yield, a dye that dyes paper a considerably more brilliant shade than the corresponding dye synthesised without use of the protecting group.

The corresponding dyes having a free amino group can be obtained in analogous manner from the precursors described in Examples 3 to 10, 12, 13, 18, 19, 23, 25, 27, 29, 35, 37, 41, 44, 51, 56 and 57. 

1. A dye of formula

wherein Z₁ is NHR₆, R₆ being a radical of formula CO—NH—R₈, SO₂-alkyl or COOR₈, R₈ being hydrogen, alkyl or aryl and Z₂ is as defined for Z₁ or is hydrogen, hydroxy, alkoxy or a radical NHR₅, R₅ being hydrogen, alkyl, aryl, COR₈, CO—NHR₈ or SO₂R₈, R₁ and R₃ are each independently of the other hydrogen, hydroxy, alkyl or alkoxy, R₂ and R₄ are each independently of the other hydrogen, hydroxy, alkyl or alkoxy, halogen, sulfo, carboxy, NHCONHR₈ or NHCOR₈, X is azo, azoxy, —NR₈—, —NR₈CONR₉— or a group of formula

Y being hydroxy, alkoxy or NR₉R₁₀, R₉ and R₁₀ being each independently of the other hydrogen, unsubstituted or substituted alkyl or unsubstituted or substituted aryl, n and m are each independently of the other 1 or 2, and wherein the rings A and B may each independently of the other carry a fused-on benzene ring.
 2. A dye according to claim 1, wherein Z₂ is hydrogen, hydroxy, alkoxy, amino, NH—COO—C₁–C₄alkyl, or anilino which is unsubstituted or substituted by amino and/or by sulfo.
 3. A dye according to claim 1, wherein Z₁ is NH—COO—C₁–C₄ alkyl.
 4. A dye according to claim 1, wherein Z₁ and Z₂ are identical and each is NH—COO—C₁–C₄ alkyl.
 5. A dye according to claim 1, wherein R₂ and R₄ are each hydrogen, C₁–C₄alkyl or C₁–C₄alkoxy.
 6. A process for the preparation of a dye of formula (1) according to claim 1, wherein a diamine of formula

is tetraazotised and coupled with 2 moles of a coupling component of formula

or with 1 mole each of a coupling component of formula (4) and of formula

under conditions known per se.
 7. A process for the preparation of a dye of formula (1′),

wherein Z₁, and Z₂ are each independently of the other amino and the other substituents are as defined for a dye of formula (1) in claim 1, in which process there are used dyes of formula (1) wherein Z₁ and Z₂ are each independently of the other NH—COO—R₈, and finally that group is hydrolysed.
 8. A method for dyeing paper, which comprises contacting the paper with a tinctorially effective amount of a dye of formula

wherein Z′₁ is NHR₈, R₆ being a radical of formula —CO—NH—R₈, SO₂-alkyl or COOR₈, R₈ being hydrogen, alkyl or aryl and Z′₂ is as defined for Z′₁ or is hydrogen, hydroxy, alkoxy or a radical NHR₅, R₅ being hydrogen, alkyl, aryl, COR₈, CO—NHR₈ or SO₂R₈, R₁ and R₃ are each independently of the other hydrogen, hydroxy, alkyl or alkoxy, R₂ and R₄ are each independently of the other hydrogen, hydroxy, alkyl or alkoxy, halogen, sulfo, carboxy, NHCONHR₈ or NHCOR₈, X is azo, azoxy, —NR₈—, —NR₈CONR₉— or a group of formula

Y being hydroxy, alkoxy or NR₉R₁₀, R₉ and R₁₀ being each independently of the other hydrogen, unsubstituted or substituted alkyl or unsubstituted or substituted aryl, n and m are each independently of the other 1 or 2, and wherein the rings A and B may each independently of the other carry a fused-on benzene ring.
 9. A solid dye preparation for dyeing paper, comprising dye of formula (1) according to claim 1 and, optionally, further additives.
 10. A concentrated aqueous solution for dyeing paper, comprising a dye of formula (1) according to claim 1 and, optionally, further auxiliaries.
 11. Paper dyed using a dye of formula (1) according to claim
 1. 12. A dye according to claim 2, wherein Z₁ is NH—COO—C₁–C₄alkyl.
 13. A dye according to claim 3, wherein Z₁ and Z₂ are identical and each is NH—COO—C₁–C₄alkyl.
 14. A dye according to claim 4, wherein R₂ and R₄ are each hydrogen, C₁–C₄alkyl or C₁–C₄alkoxy.
 15. Paper dyed using a solid dye preparation according to claim
 9. 16. Paper dyed using a concentrated aqueous solution according to claim
 10. 